Probe for a scanning probe microscope and method of manufacture

ABSTRACT

A probe assembly for an instrument and a method of manufacture includes a substrate and a cantilever having a length independent of typical alignment error during fabrication. In one embodiment, the probe assembly includes a buffer section interposed between the substrate and the cantilever. The cantilever extends from the buffer section and a portion of the buffer section extends beyond an edge of the substrate. The portion of the buffer section is more stiff than the cantilever. The corresponding method of producing the probe assembly facilitates batch fabrication without compromising probe performance.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed to a probe assembly for a metrologyinstrument used to measure a property of a sample, and moreparticularly, a probe assembly including a cantilever having a shortlength to support high bandwidth operation, and configured for readybatch fabrication.

2. Description of Related Art

Scanning probe microscopes (SPMs), such as the atomic force microscope(AFM), are devices which use a sharp tip and low forces to characterizethe surface of a sample down to atomic dimensions. Generally, the tip ofthe SPM probe is introduced to the sample surface to detect changes inthe characteristics of the sample. By providing relative scanningmovement between the tip and the sample, surface characteristic data canbe acquired over a particular region of the sample and a correspondingmap of the sample can be generated.

In an AFM, for example, in a mode of operation called contact mode, themicroscope typically scans the tip, while keeping the force of the tipon the surface of the sample generally constant. This is accomplished bymoving either the sample or the probe assembly up and down relativelyperpendicularly to the surface of the sample in response to a deflectionof the cantilever of the probe assembly as it is scanned across thesurface. In this way, the data associated with this vertical motion canbe stored and then used to construct an image of the sample surfacecorresponding to the sample characteristic being measured, e.g., surfacetopography. Similarly, in another preferred mode of AFM operation, knownas TappingMode™ (TappingMode™ is a trademark owned by the presentassignee), the tip is oscillated at or near a resonant frequency of theassociated cantilever of the probe. The amplitude or phase of thisoscillation is kept constant during scanning using feedback signals,which are generated in response to tip-sample interaction. As in contactmode, these feedback signals are then collected, stored and used as datato characterize the sample.

The deflection of the cantilever in response to the probe tip'sinteraction with the sample is measured with an extremely sensitivedeflection detector, most often an optical lever system. In such opticalsystems, a lens is employed to focus a laser beam, from a sourcetypically placed overhead of the cantilever, onto the back side of thecantilever. The backside of the lever is reflective (for example, usingmetalization during fabrication) so that the beam may be reflectedtherefrom towards a photodetector. The translation of the beam acrossthe detector during operation provides a measure of the deflection ofthe lever, which again is indicative of one or more samplecharacteristics.

One area of continuing SPM development relates to the speed ofoperation. In this regard, the greater the resonant frequency of thecantilever of the probe of the probe assembly the greater the speed atwhich the SPM can be operated to acquire sample surface data. One way inwhich high operational resonant frequencies, and thus improved SPMimaging speed, can be facilitated is by using a probe having acantilever that is much shorter than the typical length of about 100-400microns. This is due to the fact that, with a shorter lever, theinstrument can be operated at a higher resonant frequency with lessnoise. Therefore, keeping the same spring constant, one can operate theSPM faster while obtaining high integrity data given a greater signal tonoise ratio. Preferably, a probe having a cantilever that is less than50 microns or even less than 20 microns is preferred for suchapplications.

One significant drawback associated with using probes having shortcantilevers, however, is that for a number of reasons it is verydifficult to bulk manufacture probes having cantilevers with such shortlengths, i.e., in the sub-50 micron range. In most such processes, thelever is formed, as well as the tip, using micro fabrication techniquesthat require precise alignment of the manufacturing tools (e.g.,photolithography masks, etc.) and precise processing of the probecomponents, including bonding a substrate to the formed probe prior todicing the substrate into individual probe assemblies. In the latterregard, when producing short levered probes, it is nearly impossible toaccurately control the dicing from the backside of the batch fabricatedprobe assemblies given alignment inaccuracies in the process. Thiscauses an offset between the edge of the diced substrate and the tip ordistal end of the cantilever. This offset cannot be readily controlled.As a result, probe assemblies having profiles such as that shown inFIGS. 1A-1C may result. In particular, for example, FIG. 1A illustratesa probe assembly 15 having a lever 16 with a length about 30 microns, asdesired. However, given alignment inaccuracies and related complicatingfactors during fabrication, the probe assembly 15′ of the next batch maybe formed such that the glass substrate 18 bonded to the probe yields nocantilever, such as that shown in FIG. 1B. Finally, in the next batch,as shown in FIG. 1C, the probe assembly 15″ may have a cantilever 16′with a significantly greater length, such as 60 microns. In sum, theoffset from the edge of the substrate to the tip upon bonding and dicingthe substrate, hereinafter called the “uncontrollable offset”, yields acantilever having a length that cannot be predictably controlled,assuming the cantilever is formed at all.

In this regard, two specific types of probes employing silicon nitridecantilevers are shown in FIGS. 2A (glass substrate) and 2B (siliconsubstrate). In FIG. 2A, a probe assembly 20 includes a probe 21 having asilicon tip 22 and a silicon nitride lever 24 that extends from a glasssubstrate 26. In this case, the substrate 26 is bonded directly to thesilicon nitride that forms and defines the length of cantilever 24. As aresult, when batch fabricating such a probe, the uncontrollable offset,“O”, as shown in FIG. 2C, present when the probes are diced operates tolimit the manufacturer's ability to produce repeatable probe assemblieshaving a short, for instance, sub-20 micron, length. More particularly,standard mechanical dicing operations have inherent alignment errors(typically, as much as tens of microns) that, though acceptable forfabricating conventional probes, is unacceptable for fabricating thetype of short probes contemplated herein. In FIG. 2B, a self-actuatedprobe assembly 30 includes a probe 32 having an integrated actuator 34and a base substrate 35 made of silicon. A cantilever 36 of probe 32made of silicon extends from actuator 34 defined by top and bottom goldelectrodes 38, 40, respectively, and an active element 42, such as zincoxide. Here again the substrate 35 is bonded directly to the siliconnitride layer, or electrode 38, that defines cantilever 36. In thiscase, the individual probe assemblies are released with an appropriateetch of the sacrificial silicon. Due to processing limitations,performing this etch with sufficiently high precision tocost-effectively define cantilevers 36 having repeatable lengths in thesub-20 micron scale is generally impossible, as understood in the art.In particular, in this case, the length of the cantilever is typicallydefined by front-side and back-side etches of the substrate. It is verydifficult to control these etches to define short (e.g., sub-20 micron)levers because of orthogonality and parallax considerations, asunderstood in the art.

In view of the above, the art of scanning probe microscopy was in needof a probe assembly having a short lever, i.e., less than 20 microns,and a corresponding method of batch fabricating the probe such that thelength of its associated cantilever can be precisely controlled andbatch processed independent of inherent alignment errors associated withfabrication processes in which the probes are either diced or etched.This control of the length of the cantilever should be realized withoutcompromising the physical properties of the probe. For instance, thespring constant must be maintained so that the probe is capable ofoperating at high bandwidth, thus allowing the SPM to perform high speedimaging.

Note that “SPM” and the acronyms for the specific types of SPMs, may beused herein to refer to either the microscope apparatus, or theassociated technique, e.g., “atomic force microscopy.”

SUMMARY OF THE INVENTION

The preferred embodiment overcomes the drawbacks of prior art systems byproviding a probe that is manufactured so that its length is independentof inherent alignment error(s) associated with the process. In oneembodiment, the probe includes a buffer section intermediate thesubstrate and the cantilever, thus eliminating the drawbacks associatedwith the uncontrollable offset (caused by alignment error during dicing)present in known techniques of batch fabricating probes. The buffersection allows the length of the cantilever to be precisely defined, inthe sub-20 micron range, and is sufficiently stiff to allow thecantilever extending therefrom to freely oscillate at high resonantfrequencies. In an alternative in which the probe is etched from thefront and back sides of a substrate, the length of the cantilever isindependent of conventional alignment errors caused by orthogonality andparallax issues during the etch fabrication process.

According to a first aspect of the preferred embodiment, a probeassembly for an instrument for imaging a sample includes a substrate, acantilever and a buffer section interposed between the substrate and thecantilever. In this case, the cantilever extends from the buffer sectionand, preferably, a portion of the buffer section extends beyond an edgeof the substrate and is more stiff than the cantilever.

According to another aspect of the preferred embodiment, the buffersection is made of silicon oxide and is at least two times thicker thanthe cantilever.

In another aspect of this embodiment, the buffer section is corrugatedand made of the same material as the cantilever.

According to a still further aspect of the preferred embodiment, theprobe assembly includes a tip, and the corrugation of the buffer sectionhas a depth not limited by a height of the tip which extends generallyorthogonally from the cantilever.

In another aspect of this embodiment, a cantilever has a thicknessbetween about 10 nm and 1000 nm and the buffer section is designed to besubstantially stiffer than the cantilever.

In yet another aspect of this preferred embodiment, the length of thecantilever is less than about 10 microns.

In an even still further aspect of the preferred embodiment, anoperational resonant frequency of the cantilever is in a range of about300 to 1000 kHz.

According to an alternate aspect of the preferred embodiment, a methodof fabricating a probe for an instrument includes forming a probeassembly having a cantilever and a tip. The method further includesproducing a buffer section, from which the cantilever extends. Themethod also includes bonding a substrate to the buffer section anddicing the substrate so that at least a portion of the buffer sectionextends beyond an edge of the substrate.

In another aspect of this embodiment, the buffer section is a layer ofsilicon oxide having a thickness substantially greater than a thicknessof the cantilever.

In yet another aspect of this preferred embodiment, the buffer sectionis corrugated so as to define a plurality of trenches having a depthselected to control the stiffness of the portion.

According to a still further aspect of the preferred embodiment, theforming step includes depositing silicon nitride on a sacrificialsilicon wafer. Preferably, the substrate is either silicon or glass.

These and other objects, features, and advantages of the invention willbecome apparent to those skilled in the art from the following detaileddescription and the accompanying drawings. It should be understood,however, that the detailed description and specific examples, whileindicating preferred embodiments of the present invention, are given byway of illustration and not of limitation. Many changes andmodifications may be made within the scope of the present inventionwithout departing from the spirit thereof, and the invention includesall such modifications.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred exemplary embodiment of the invention is illustrated in theaccompanying drawings in which like reference numerals represent likeparts throughout, and in which:

FIGS. 1A-1C are schematic side elevational views of a prior art probe,illustrating the lack of control over the position of the tip, and thusthe length of the cantilever;

FIG. 2A is a schematic elevational side view of a prior art probe;

FIG. 2B is a schematic side view of a prior art probe having anintegrated actuator;

FIG. 3 is a series of schematic side elevational illustrations showingthe steps to batch microfabricate a probe assembly according to apreferred embodiment, the bottom illustration showing the probe having ashort cantilever extending from a thick, and thus stiff, buffer section;

FIG. 4 is a perspective view of a probe assembly according to anotherpreferred embodiment of the invention, the probe having a shortcantilever extending from a corrugated buffer section;

FIG. 4A is a partially broken away cross-sectional view of thecorrugated section of the probe assembly along line 4A-4A of FIG. 4;

FIG. 5 is a series of schematic side elevational illustrations showingthe steps to batch microfabricate the probe assembly of FIG. 4;

FIG. 6 is a top plan view of a probe assembly being fabricated accordingto another preferred embodiment similar to the probe produced as shownin FIG. 5, where the corrugation is not limited by tip height;

FIG. 7 is a cross-sectional front view of the probe assembly of FIG. 6,along line 7-7;

FIG. 8 is a side elevational view of the resultant probe assemblyfabricated as shown in FIG. 6;

FIG. 9 is a series of schematic side elevational illustrations showingthe steps to batch microfabricate the probe assembly shown in FIGS. 6-8,the bottom illustration corresponding to FIG. 8;

FIG. 10 is back elevational view of a probe assembly fabricatedaccording to the present invention, similar to the probe of FIGS. 6-9but having pyramid shaped corrugation, similar to the probe of FIG. 4;

FIG. 11 is a perspective view of the probe assembly illustrated in FIG.10; and

FIG. 12 is a series of schematic side elevation illustrations showingthe steps to batch microfabricate a probe assembly according to anotherpreferred embodiment of the invention using offset alignment, the bottomillustration showing a probe having a controllable short cantilever.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Turning initially to FIG. 3, the bulk production of a probe assemblyhaving a short, sub-20 micron cantilever, is illustrated in a series offabrication steps. Moving from top to bottom, the process is initiatedwith a sacrificial silicon wafer 100 provided in step A. Then, a bufferlayer 102 is deposited on the back side of wafer 100 in step B. Bufferlayer 102 may be a silicon oxide or a silicon nitride, for instance, andwill interface the flexible cantilever of the probe, described furtherbelow. Layer 102 is designed to be much stiffer than the cantilever thatwill ultimately extend therefrom, and facilitates batch fabrication ofthe probe assembly by eliminating the uncontrollable offset that canresult when dicing the probes, and specifically the substrate coupled tothe probe during process. This stiffness is preferably achieved byforming layer 102 to have a significantly greater thickness than thelayer that will become the cantilever. For instance, the thickness oflayer 102 can be about 1-2 microns, but it can be much larger ifdesired. Overall, the stiffness of the buffer layer 102 is preferablyabout an order of magnitude greater than that of the cantilever.

Next, in step C the buffer layer 102 is etched to an appropriate point104 relative to an end point 105 of wafer 100 so as to form a buffersection 106 and expose wafer 100 for forming a pit 107 in step D toaccommodate a tip of the probe. Notably, this etch is performed usingstandard planar processing used, for example, in semiconductorfabrication processes. As understood in the art, such processes arehighly precise. Then, a thin layer 108 of silicon nitride is disposed onbuffer layer 102 and the exposed portion of silicon wafer 100 in step Eso as to form a cantilever 109 which will be released as part of theprobe assembly in a later step. This layer 108 of nitride isapproximately 10-1000 nm thick to provide a flexible cantilever 109having an appropriate spring constant. Preferably, the spring constantsof the short cantilevers of the preferred embodiments are similar to thespring constants of conventional AFM probes to maintain performance. Forexample, the resonant frequency of a standard TappingMode™ cantilever istypically about 300 kHz. To do so, the thickness of the levers arepreferably reduced to accommodate their shorter length. Also in step E,a thin layer of silicon nitride will be deposited in pit 107.

In the next step of the fabrication process, step F, a glass (orsilicon) substrate 110 is bonded to the silicon nitride layer 108 thatdefines cantilever 109 such that substrate 110 is coupled to cantileverwith at least a portion of buffer layer 102 intermediate the two.Preferably, the bonding is accomplished using conventional bondingtechniques. Thereafter, the probes are cut or diced in step G. It isthis step, as discussed previously, that is difficult to control due toan inherent alignment error associated with the mechanical equipmentused to dice the substrate, i.e., it is this error that results in whatmay be called an uncontrollable offset, labeled “O” in step G. Byensuring that this portion of buffer section 106 is stiff (together withthe precise etch of step C), the cantilever extending therefrom can beformed with a precise length while maintaining the physical propertiesof the probe. More particularly, given the use of buffer section 106,the dicing operation has generally no impact on controlling the lengthof the lever 109, the fixed end of the cantilever 109 having beendefined when etching the thick buffer layer 102 to form buffer section106. Finally, in step H, the resultant probe assembly 114 according tothis embodiment is completed by a silicon etch to remove the silicon ofthe initial sacrificial wafer 100.

Again, given its thickness, the flexibility of buffer section 106 isnegligible compared to the flexibility of the silicon nitride cantilever109 (lever 109 having a spring constant “k” preferably equal to a rangeof about 0.005 to 100 N/m). This embodiment is particularly adapted foruse with a glass substrate.

Turning to FIG. 4, an alternate probe assembly 150 according to thepresent invention includes a probe 151 and a buffer section 152 that isproduced so as to have a corrugated shape. In this case, buffer section152 is formed by etching a base silicon wafer and depositing, forexample, a silicon nitride layer thereafter, as described in furtherdetail below in connection with FIG. 5. A cantilever 154 is alsoproduced via the deposition of the silicon nitride and extends fromsection 152 so that it may flex about its base 156 defining theinterface between cantilever 154 and buffer section 152. As usual,cantilever 154 includes a distal end 158 from which a tip 160 extendsgenerally orthogonally for interacting with a surface of a sample undertest (not shown).

Corrugated buffer section 152 includes a plurality of trenches 162 thatoperate to stiffen probe 150 in a region of the probe assembly 150defining the uncontrollable offset associated with producing probeshaving short cantilevers, described previously. As a result, the moreflexible cantilever 154 extending therefrom is defined in a region wherethe length of the lever can be predictably controlled, and thus batchreproduced. In between trenches 162 lie flat portions 164 that areadapted for ready bonding of a glass or silicon substrate thereto.

Ideally, base 156 of cantilever 154 is rigidly fixed to buffer section152 such that, for instance, cantilever oscillation in TappingMode™ doesnot include any corresponding movement of buffer section 162. Therefore,buffer section 162 should be as stiff as possible. In this regard, thedepth of trenches 162 at least partially defines the stiffness of buffersection 152. However, given processing constraints associated withforming trenches 162 on the same side of the wafer as tip 160, the depthof trenches 162 is limited to the height of the desired tip 160.Therefore, because tip heights are typically small, at least smallerthan trench depth that would provide ideal stiffness to buffer section152, this limitation may hinder ideal performance in certainapplications. In this regard, one possible alternative is illustrated inFIGS. 6-9, discussed below. Overall, an uncontrollable offset of probeassembly 150 is defined by corrugated buffer section 152, which is not afactor in batch fabricating the probe assemblies having short, sub-20micron cantilevers 154.

Turning to FIG. 5, the fabrication of probe assembly 150 is illustratedas a series of process steps. Initially, at step A, a sacrificial wafer170 is provided. Then, at step B, the corrugated buffer section isselectively patterned to produce the series of trenches, as well as theprobe tip at locations 172 and 174, respectively. At this point, step C,a thin silicon nitride layer 176 is deposited to, inter alia, form thecantilever. Layer 176 has a thickness of about 100 nm. Thereafter, asubstrate 178 is bonded to the silicon nitride according to knowntechniques at step D of the process. At step E, the wafer is diced intoindividual probe assemblies using standard alignment procedures.Notably, at this point, an offset labeled “O”, which again cannot bereadily controlled due to imperfect alignment of the mechanical dicingapparatus relative to the probe (i.e., alignment error), is defined.However, as noted in connection with the previous embodiment illustratedin FIG. 3, the length of the cantilever is not controlled by this dicingoperation and thus the bulk processing problem associated with theuncontrollable offset present in standard techniques is avoided. Thelength of the cantilever is instead defined in part by an end point ofthe trenches, a known position relative to tip. Notably, a portion ofcorrugated buffer section 152 at step “E” is shown in FIG. 4A, whereinthe silicon trenches include a thin layer of silicon nitride 176.

Finally, at step F, the silicon wafer 170 is etched from the front sideto expose a lever 182 and a tip 184. Tip 184 is preferably siliconnitride, and is defined by a thin shell. As a result, a probe assembly180 having a corrugated buffer section 186, a portion 190 of whichextends beyond an edge of substrate section 188 is produced. Cantilever182 extends from buffer section 186 at a point “X” about which thecantilever can oscillate, as in TappingMode™. Again, the depth of thetrenches of corrugated section 186 is limited by the height of tip 184,as appreciated by those skilled in the microfabrication art.

Turning to FIGS. 6-8, a probe assembly 200 fabricated from a siliconwafer 202 is shown. Probe assembly 200 is similar to probe assembly 180shown in FIG. 5. However, in this case, a corrugated buffer section 204of probe assembly 200 is formed on a side of wafer 202 opposite the sidewhere a tip 206 of probe assembly 200 is formed, and thus buffer section204 may have a greater range of depths “d” (see FIG. 7), and thus agreater range of stiffnesses than the probe assembly shown in FIG. 4. Inaddition, the cross-sectional shape of the series of trenches 208 ofbuffer section 204 is rectangular rather than pyramid-shaped.

Probe assembly 200 includes a cantilever 210 extending from the rigidbuffer section 204 at about a fixed point 205. With further reference toFIGS. 6 and 8, cantilever 210 also includes a distal end 207 oppositefixed end or point 205 which supports tip 206 that is used forinteracting with a surface of a sample in conventional fashion. Probeassembly 200 also includes a glass substrate 212 upon dicing the waferto form the individual probe assemblies prior to releasing the probesfrom the wafer, described in further detail below with respect to FIG.9.

Preferably, as shown in FIGS. 7 and 8, trenches 208 are formed in thesilicon wafer 202 opposite the side used to form the pit for tip 206. Asa result, more design flexibility is realized in terms of achievablestiffness of buffer section 204. The length of the buffer section 204,defined at least in part by the bonded and diced glass substrate 212 anda fixed end 205 of probe 202, generally corresponds to what has beendescribed earlier as the uncontrollable offset “O” associated with knownprobe fabrication techniques. Because the length of probe 200 is notcontrolled by the dicing of the substrate 212, this offset is not theproblem it is in known techniques, and thus bulk fabrication of probeassemblies 200 is facilitated.

To form probe 200 reference is made to FIG. 9. Similar to the previousprobes, the process starts with a sacrificial silicon wafer 250 at stepA. A wet or dry etch is then employed at step B, for instance, from theback side of wafer 250, to form a corrugated buffer section 251 definedby a series of trenches 252. Notably, the length “1” of trenches 252 canbe precisely controlled using known techniques. Next, in step C, a pit254 for forming a tip is etched in wafer 250. A thin layer 255 ofsilicon nitride is then deposited on the etched wafer in step D.Thereafter, a substrate 256 (glass or silicon) is bonded to trenches 252of wafer (step E), and then cut to form the individual probe assembliesin step F. An uncontrollable offset associated with this step E is shownat “O” for illustrative purposes. To the contrary, a length “L” of aresultant cantilever 258 can be precisely controlled, again due to thefact that the dicing of the probes does not control cantilever length;rather, edges of wafer 250 and corrugated buffer section 251 definecantilever length, which may be on the order of less than 20 microns,and preferably less than 10 microns. Finally, in step G, the sacrificialsilicon 250 is etched to release the probes.

In an embodiment similar to that discussed immediately above, a probeassembly 300 including a corrugated buffer section 302 is formed havinga series of pyramid-shaped, as opposed to rectangular, trenches 304 incross section, as shown in FIGS. 10 and 11. The process steps areotherwise identical to that shown in FIG. 9.

In a still further embodiment of bulk microfabricating a probe with ashort cantilever, an offset alignment technique is employed in theprocess steps shown in FIG. 12, for an etch released, rather than diced,probe. In step A, a sacrificial wafer 320 is provided. In step B, a pit322 for defining a probe tip is formed, for example, using nanodot and(111) plane overetch techniques. In addition, a silicon nitride layer324 is deposited. Next, in step C, a substrate 326 is bonded to layer324, for example, using fusion wafer bonding. The sacrificial wafer isthen stripped using an appropriate etch, and a silicon nitride layer 328is applied to the substrate in step D. In step E, an “offset alignment”technique is employed, including initially etching the silicon nitridefrom the front and back sides of the substrate to points U and V,respectively, a non-planar process. Again, it is this non-planar etchingprocess that is difficult to control due to orthogonality and parallaxconsiderations (which cannot be readily minimized) present duringdefining the length of the lever with the etches. An alignment error (asmuch as tens of microns) between the front and back side etches results,and thus short levers are difficult to repeatedly produce, as understoodin the art.

In this embodiment, etching is accomplished with precisephotolithographic patterning, for instance, to ultimately define thelength of the lever with the following etch of the substrate 326. Inparticular, using a KOH etch in step F to etch to the (111) plane of thesilicon substrate 326 at fifty-four point seven degrees (54.7°), asunderstood in the art, the alignment error is substantially eliminatedand the length of a cantilever 330 of a probe 329 produced thereby canbe repeatedly produced in bulk.

Although the best mode contemplated by the inventors of carrying out thepresent invention is disclosed above, practice of the present inventionis not limited thereto. It will be manifest that various additions,modifications and rearrangements of the features of the presentinvention may be made without deviating from the spirit and scope of theunderlying inventive concept.

1. A probe assembly for a surface analysis instrument, the probeassembly comprising: a substrate defining a base of the probe assembly;a cantilever extending from the base and having a distal end; wherein alength of said cantilever is independent of alignment error during probefabrication.
 2. The probe assembly of claim 1, further comprising abuffer section interposed between said substrate and said cantilever,said cantilever extending from said buffer section.
 3. The probeassembly of claim 2, wherein a portion of said buffer section extendsbeyond an edge of said substrate, and wherein said portion is more stiffthan said cantilever, and wherein said buffer section is made of one ofsilicon nitride and silicon oxide.
 4. The probe assembly of claim 3,wherein said buffer section is at least two times thicker than saidcantilever.
 5. The probe assembly of claim 2, wherein said buffersection is made of the same material as said cantilever.
 6. The probeassembly of claim 2, wherein a stiffness of said buffer section is in atleast about an order of magnitude greater than a stiffness of saidcantilever.
 7. The probe assembly of claim 6, wherein a stiffness ofsaid buffer section is in a range of about 10 to 50 N/m.
 8. The probeassembly of claim 2, wherein said cantilever has a thickness less thanabout 1000 nm.
 9. The probe assembly of claim 8, wherein said cantileverhas a thickness less than about 100 nm.
 10. The probe assembly of claim3, wherein said portion of said buffer section is at least about 10times as stiff as said cantilever.
 11. The probe assembly of claim 1,wherein said substrate is one of silicon and glass, and wherein anoperational resonant frequency of said cantilever is in a range of about300 to 1000 kHz.
 12. The probe assembly of claim 1, wherein a length ofsaid cantilever is less than about 50 microns.
 13. The probe assembly ofclaim 12, wherein the length is less than about 10 microns.
 14. A methodof fabricating a probe assembly for a surface analysis instrument, themethod comprising: forming a probe of the probe assembly, the probeincluding a cantilever; and wherein a length of the cantilever isindependent of an alignment error associated with said forming step. 15.The method of claim 14, wherein said forming step includes forming atleast a portion of the probe assembly on a substrate and dicing thesubstrate to release the probe assembly, wherein said dicing step isresponsible for the alignment error.
 16. The method of claim 15, furthercomprising, producing a buffer section; and wherein said forming stepincludes disposing a layer of a cantilever material on the buffersection such that the cantilever extends from the buffer section, andwherein said dicing step is performed so that at least a portion of thebuffer section extends beyond an edge of the substrate.
 17. The methodof claim 16, wherein the buffer section is a layer of material having athickness substantially greater than a thickness of the cantilever. 18.The method of claim 17, wherein the layer of material is silicon oxide.19. The method of claim 16, wherein a stiffness of said buffer sectionis at least an order of magnitude greater than a stiffness of saidcantilever.
 20. The method of claim 16, wherein said cantilever is lessthan 100 nm thick.
 21. The method of claim 16, wherein a length of thecantilever is less than 20 microns.
 22. The method of claim 21, whereina length of the cantilever is less than 10 microns.
 23. The method ofclaim 18, wherein the cantilever material is silicon nitride, andwherein the substrate is one of silicon and glass.
 24. The method ofclaim 23, wherein said forming step includes depositing the siliconnitride on the substrate, and the substrate is a sacrificial siliconwafer.
 25. The method of claim 14, wherein said forming step includesperforming an offset alignment technique to define the length of thecantilever.
 26. The method of claim 25, wherein said performing stepfurther includes, providing a sacrificial wafer, shaping a tip in thewafer, then depositing a cantilever material on the wafer, wherein saidcoupling step includes bonding the substrate to the cantilever material;removing the wafer; and applying a layer of a material to the substrateopposite the cantilever material.
 27. The method of claim 26, whereinsaid shaping step includes using a nanodot and plane overetch technique.28. The method of claim 26, wherein said removing step includes etchingthe wafer, and wherein said bonding step includes fusion wafer bonding.29. The method of claim 26, wherein the cantilever material and thematerial layer are silicon nitride.
 30. The method of claim 26, whereinsaid performing step includes patterning the probe, etching thecantilever material and the material layer, and then etching thesubstrate.
 31. The method of claim 28, wherein said etching thesubstrate step includes a KOH etch to the (111) plane.
 32. The method ofclaim 26, wherein the probe has a length less than 20 microns.